KR20180132647A - Graphite-containing article - Google Patents

Abstract

Cookware and other heated articles are included herein. The article may have a substrate forming a lower surface of the cookware. The article may also have a cooking / heating surface disposed over the graphite intermediate and intermediate layers. The graphite layer may have one or more of the following properties; (1) a density of at least 0.64 g / cm < ³ >; (2) less than 30% water pick-up after immersion for 2.5 hours in water at ambient conditions; (3) Taber stiffness at least 25% higher in the machine direction than in the transverse direction; And (4) a sulfur content of less than 350 ppm, and combinations thereof.

Description

Graphite-containing article

This disclosure relates to the field of articles used in cooking or heating apparatus, and specific examples such as cookware articles or experimental apparatus comprising an intermediate layer of graphite.

Prior art types of cookware include: (1) a high ferritic stainless steel composition designed for induction cooking; (2) ordinary stainless steel designed for conductive heating; (3) metals coated or coated with high ferritic stainless steel for induction cooking; And (4) glass or ceramic cooking utensils.

The embodiments disclosed herein include cooking utensils as well as other articles that can be used to heat objects. In one embodiment, the article may have a substrate comprising a lower surface of the cookware. The cooking utensil may also have a cooking surface disposed over the graphite intermediate layer and the intermediate layer. Preferably, the graphite layer may have one or more of the following properties: (1) a density of at least 0.64 g / cm < ³ >; (2) less than 30% water pick-up after immersion in water for 2.5 hours in ambient conditions; (3) Taber stiffness at least 25% higher in "machine direction" than in "transverse"; And (4) a sulfur content of less than 400 ppm. Optionally, the graphite may have any combination of these properties.

It is to be understood that both the foregoing general description and the following detailed description are exemplary and explanatory and are intended to provide further explanation of the nature and character of the invention as claimed. The accompanying drawings are included to provide a further understanding of the invention, and are incorporated in and constitute a part of this specification. The drawings illustrate various embodiments of the invention and, together with the description, serve to explain the principles and operation of the invention.

Figure 1A shows an embodiment of the graphite article disclosed in the specification which can be used for heating;
Figure IB shows another embodiment of a graphite article having the wire mesh disclosed herein.
Fig. 2 is a perspective view in which a standard cooking utensil used for heating the contents of the standard cooking utensil is combined with the embodiment of Fig.
FIG. 3 is an interior view of the embodiment of FIG. 1A in the cooking apparatus,
Figure 4 is a partial cross-sectional view of another embodiment described herein,
Figure 5 is a partial cross-sectional view of a further embodiment described herein,
Figure 6 is a schematic view of the embodiment disclosed herein showing induction heating that can be used for cooking,
FIG. 7A is a table (Table IIa), FIG. 7B is a table (Table IIb), and the two tables represent time conditions for boiling for an embodiment of the graphite article disclosed herein.

One embodiment disclosed herein includes a cookware article. The cookware article may have a substrate comprising a lower surface of the cookware. The cooking utensil further includes an intermediate layer including a graphite layer and a cooking surface disposed above the intermediate layer. The graphite layer may comprise at least one of a sheet of compressed exfoliated graphite particles, a graphitized polymer, or a combination thereof. Optionally, the intermediate layer may comprise a plurality of graphite sheets in any combination thereof.

Graphite layer may have one or more of the following characteristics: (1) a density of at least 0.64 g / cm ^3, up to 2.25 g / cm ³ (including any density in between); (2) water absorption of less than 30% by weight, preferably less than 28% by weight after immersion for 2.5 hours in water at ambient conditions; (3) Taber stiffness at least 25%, preferably at least 30% higher in "machine direction" than in "transverse"; And (4) a sulfur content of less than 375 ppm, preferably less than 250 ppm and more preferably less than 200 ppm. The Leco S-144DR can be used to measure the sulfur content of the sample. Reco S-144DR is a system for analyzing the total sulfur content of a given sample. Its minimum detection limit is approximately 50 ppm. Equipment for measuring the tape stiffness is available from Taber Industries, Inc., North Tonnawanda, New York, USA. Water absorption can be determined by measuring the change in the weight of the graphite layer before and after immersion in water under certain conditions.

In a particular embodiment, the graphite article includes an effective amount of a magnetosensitive material that allows it to successfully couple to an applied magnetic field generated with sufficient power delivered by a frequency of at least 15 KHz in a manner that generates heat. In one embodiment up to about 50 KHz, and possibly up to 70 KHz. An example of a sufficient amount of graphite is a graphite layer having a thickness of at least 7 micrometers. In at least one exemplary embodiment, the upper limit of the thickness may be about 5 mm. An example of the maximum frequency used for cooking is 100 KHz or less.

In a further embodiment, the graphite layer of the intermediate layer has a surface area that includes at least 7 square inches (7-in ² ). Typically, the graphite layer will not have a surface area exceeding 1 m ² (1 m ² ). An example of a specific footprint size for a graphite layer is typically 78 to 452 square inches (in ² ) for a 5 inch (12 ") diameter fan. Some specific examples include graphite layers with a footprint in the range of 300 to 390 square inches (in ² ).

In yet another embodiment, the graphite layer may be in the form of a single article compacted together from a graphite disk having a diameter of 3 inches to 12 inches (3 "to 12"). The article may be formed of two to ten compressed peeled graphite particle layers (2 to 10). The exemplary thickness of each graphite layer may be 5 mil at an exemplary density of 0.85 g / cm < ³ >.

In one particular embodiment, the graphite intermediate layer may function as a < RTI ID = 0.0 > antimagnet, < / RTI > exhibiting a magnetosensitivity that generates an opposite induction field of the applied applied magnetic field.

In another particular embodiment, the graphite intermediate layer is a metal (e.g., copper), aluminum, silver, iron (also known as steel) and alloys thereof that provide a means of altering the interaction of the applied magnetic field, And may be disposed in contact with another thin layer such as a film. The thickness of any particular metallic film may be from about 5 micrometers to about 0.5 mm (500 micrometers).

In another particular embodiment, the graphite intermediate layer may include one or more wire meshes embedded therein. Suitable materials for the wire mesh are aluminum, brass, copper, gold, inconel, nickel, nickel alloys, phosphors, bronzes, platinum, silver, stainless steel, low carbon steel, tantalum, titanium, zinc, zirconium, polyetheretherketone (PEEK), PTFE, PFA, ECTFE, polypropylene, polyethylene, PET (e.g., a registered trademark of miles DuPont (Dupont), La (Mylar) ^®, but not limited to), and may include a combination thereof . Including a mesh in the graphite intermediate layer allows graphite to be easily molded into a 3-D shape for introduction to other articles.

Graphite has significantly different thermal, density and magnetic properties compared to ferromagnetic materials commonly used in cookware manufacture. The cookware using graphite may have one or more of the following advantages: (1) light weight, (2) thermal response, and (3) thermally uniform cooking. These benefits can work well in all surface cooking techniques (e.g., gas, conventional electricity, infrared and induction cooktops). See the characteristic differences in Table 1 below.

matter In-plane thermal conductivity (W / mK) Density (g / cm ³⁾ CTE linear (10 ^-6 K ^-3 ) Specific heat capacity (J / Kg · K) The molar heat capacity (J / mol · K) Volume specific heat capacity Substantial self-susceptibility black smoke 300-2000 0.64-2.27 0.5 0.71 0.0085 0.0192 Yes Copper 385 8.96 17 0.39 0.0244 7.9022 Special situation aluminum 205 2.70 23.1 0.90 0.0243 2.3651 no Stainless steel (1810) 16-21 7.99 17.3 0.50 0.0277 7.9900 no Steel (high ferrite steel) 50 7.87 11.8 0.44 0.0246 6.9768 Yes Glass 0.8 2.4-2.8 0.33 0.84 0.0505 4.5515 no

Other important properties of graphite in relation to the embodiments described herein include molar heat capacity and volume specific heat capacity. This property can be a good indicator of how quickly a particular material gets and releases heat, indicating the thermal response of graphite.

An alternative type of graphite may include at least one of isomolded graphite, extruded graphite, graphite foam, molded graphite, or combinations thereof.

Optionally, the cookware article may further comprise a thermal insulation material disposed between the substrate and the intermediate layer. Insulating materials that may optionally be included in the cookware include airgel, glass-wool, fiberglass, carbon fiber, carbon foam, hot plastic or ceramic insulation, and / or graphene.

The substrate may contain an amount of ferromagnetic material that is insufficient to cook by induction. Alternatively, the substrate may comprise a non-magnetic material. For purposes of this disclosure, a non-magnetic material is a material that does not react to applied magnetic fields in a manner that generates a notable thermal response for cooking / heating. A material may be considered non-magnetic for cooking or heating purposes if the article produced therefrom generates a heat rise of less than 2 ° C per minute at a given initial condition of standard temperature and pressure.

In yet another embodiment, the substrate may have a through plane thermal conductivity of less than about 75 W / mK. Non-limiting examples of such materials include, but are not limited to, the respective thermal stability limits (i. E., Melting point or melting point) of low ferrite stainless steel, glass (e.g., borosilicate glass), ceramic, plastic, cork, Decomposition temperature) does not produce energy above the threshold. These embodiments may be practiced together or separately. When a material with a higher thermal conductivity is desired, the option may include aluminum, copper, silver, and / or other metals and alloys thereof.

Examples of suitable cooking utensils for the above embodiments include a baking pan, a pot, a frying pan, a cooker, a grill, a popcorn maker, a coffee pot, a teapot, a coffee mug, a saute pan and a soup dish. Cookware can be used for convection, conduction, infrared or induction heating. The concepts disclosed herein may also be applied to a cooking surface, such as an oven cooktop or a range top stove. In this embodiment, the graphite layer will be the middle layer between the bottom layer and the top surface. The upper surface can function as a heat-transfer layer to the article to be heated, not the actual surface in contact with the liquid or food to be cooked.

In a particular embodiment of the cookware, the substrate comprises a structrual architecture for supporting the graphite intermediate layer. The structure contains an insufficient amount of a magnetosensitive material to produce a thermal response suitable for cooking upon exposure to a magnetic field, whereby the magnetic field passes through the structure. Graphite in the intermediate layer has an effective amount of magnetosensitive upon exposure to a magnetic field. Self-susceptibility generates heat that is conducted to the cooking surface of the cookware, thereby transferring heat from the cookware to the food or other materials that need to be cooked or heated.

The optional insulating material in the cookware can be used in a variety of ways, for example with respect to a cooking utensil with sidewalls, the insulating material can be evenly distributed throughout the sidewall. In another alternative embodiment, the insulating material may be uniformly disposed below the intermediate layer or non-uniformly below the intermediate layer. In a further alternative embodiment, the insulating material may extend along the thickness of the intermediate layer.

Embodiments of the cookware disclosed herein may include any of the aforementioned graphites embedded in aluminum or other ferritic stainless steel or other metals or alloys that do not generate heat above the threshold due to their magnetic properties upon exposure to the aforementioned magnetic fields . This embodiment applies in particular to at least the following types of cookware: boiling auxiliary plates, cookware adapters, diffuser plates, hot soup bowls, food serving utensils, barber dishes, popcorn makers, induction grill heating elements, Induction coffee pots, induction teapots, induction-available coffee mugs and induction-available food storage containers as well as the types of cookware mentioned above.

Another embodiment of the cooking utensils disclosed herein includes borosilicate glass, aluminosilicate glass, oxide glass, glass ceramics, or other materials such as buried in a high temperature glass or ceramic material to enable the generation of heat through exposure to the magnetic field And the above-mentioned graphite. This embodiment is also applicable to the above-described type of cookware described in the above paragraph. Additional embodiments applicable to cookware of at least this type include high density or low density polyethylene (HDPE or LDPE), other high temperature plastics, or high temperature plastic composites (e.g., high density polyethylene or high density polyethylene) to enable heat generation through exposure to a magnetic field. Graphite fiber composite). ≪ / RTI >

The graphite disclosed herein can have a unique combination of favorable material properties: (1) coupling with magnetic fields, (2) thermal diffusion, (3) required heat capacity And (4) lower density compared to other potential materials (promoting lightweight articles).

The concepts disclosed herein are further illustrated and described in accordance with the drawings. Referring now to FIG. 1A, an embodiment of the graphite article disclosed herein that can be used for heating is generally shown as 10 '. The graphite article 10 'may include an internal graphite section 12. Section 12 may be any desired shape. Preferably, the section 12 has a thickness of at least 7 micrometers. The section 12 may be composed of any one of the graphite types described above or a combination thereof. A trim piece 14 may surround the section 12. The rim portion 14 may preferably be made of any material that is not sufficiently bonded to the magnetic field. In addition, the rim portion 14 may be comprised of any insulating material, including, but not limited to, glass, plastic, or ceramic.

Referring now to Figure IB, another embodiment of a graphite article is generally shown at 10 ". The graphite article 10 "includes an inner graphite section 12 as described above in which a wire mesh 13 ) Are embedded. The wire mesh 13 is formed of the above-described material. It should be understood that more than one wire mesh 13 may be formed that may be formed of the same material or formed of different materials. Including the mesh 13 in the graphite section 12 allows the graphite section to be easily molded into a 3-D shape for introduction to other articles. The rim portion 14 may surround the section 12 as described above.

Graphite articles 10 'and 10 "may be generally referred to as graphite article 10.

As shown in Fig. 2, a pan 20 may be located above the article 10 for heating the material inside the pan. The graphite article 10 may be positioned on an induction-heating surface or a resistance heating surface (not shown) to apply heat to the fan 20. The graphite article 10 may be located below the fan 20 to heat the contents within the fan 20 as shown in Figure 2 or the article 10 may be heated by the fan 20, So that the contents of the fan 20 can be heated.

Figure 4 is a partial cross-sectional view of another embodiment described herein. 4 depicts a pot 40 that includes a cooking surface 42 and a graphite intermediate layer 44 and a substrate 46. As shown, the cooking surface 42 and the substrate 46 may be comprised of metal, glass, ceramic or other optional material, but any of the embodiments described above may also be applied to the pan 40. Likewise, the above description of the intermediate layer also applies to the intermediate layer 44. 5, this concept may also be applied to a port 50 that similarly includes a cooking surface 52, an intermediate layer 54, and a substrate 56. As shown in FIG.

6 is a schematic diagram of an embodiment disclosed herein showing an induction heating assembly that may be used for cooking, The induction heating assembly 60 includes an induction hob 62. The application of electricity to the induction hob 62 generally results in a magnetic field having a frequency in excess of 15 KHz.

Further, in Fig. 6, the heating element 64 may include an outer casing 66. Fig. The casing 66 may surround other components of the heating element 64. The heating element 64 may include a thermal insulation material 67 adjacent the induction hob 62. The heating element 64 may further include a graphite layer 68 adjacent the heat insulating material 67 on the opposite side of the induction hob 62. Preferably, the graphite layer 68 comprises a thickness sufficient for its magnetosensitivity to effectively combine to generate heat upon exposure to a magnetic field produced by the hob 62.

Referring now to FIGS. 7A and 7B, Tables IIa and IIb are provided which illustrate boiling time information for various embodiments of the graphite articles described herein. In the examples having from 1 to 5 layers, compressed expanded natural graphite having a sulfur content of less than 350 ppm was analyzed. Further, synthetic graphite having one to six layers was analyzed. Tables IIa and < RTI ID = 0.0 > IIb < / RTI > show the time taken to boil for the effective number of graphite layers in these examples.

The cooking implement embodiments disclosed herein may also be applied to industrial lab equipment or "lab ware" where rapid heating of liquids, gases, or solids is desired. Examples of suitable liquids may vary from water to synthetic or organic polymers. Examples of articles which can be applied outside the cookware may include the above-mentioned substrate, the above-mentioned graphite layer and an upper surface disposed on the graphite layer. Non-limiting examples of applicable articles include beakers, flasks and the like. As in the cookware embodiment, in these embodiments the graphite layer will also be an intermediate layer that exchanges heat with the working surface of the laboratory instrument in contact with the work piece (solid and / or liquid). Optionally, an insulating layer may be included adjacent to the graphite layer on the opposite side to the working surface of the instrument.

Certain critical embodiments may include articles having a graphite intermediate layer interposed between glass and / or ceramic layers. Alternatively, this embodiment may comprise a thermal insulation layer. Preferably, the insulating layer may be located adjacent to the graphite layer at a location that promotes heat transfer to the workpiece being heated or cooked. An example of such a location may include the surface of the graphite layer following the edge of the graphite layer and / or nearest the induction hob. In one embodiment, the insulation serves to optimize heat transfer efficiency in the direction of the desired thermal effect and isolate heat transfer in one or more undesired directions by isolating and inducing heat transfer in a single direction.

For industrial applications, graphite can form platens for hot pressing. Such a graphite platen can be applied to a workpiece to be squeezed. The graphite exchanges heat with the workpiece. The induction hob is also used to generate a magnetic field in exchange with the platen, generating heat for hot pressing the workpiece. Suitable types of graphite for the platen include, but are not limited to, laminate of flexible graphite (resin impregnation, non-resin impregnation and any combination thereof), isomolded graphite, molded graphite or extruded graphite, Includes appropriate grade of structural graphite. This process can be used to produce flat as well as non-planar articles. If desired, each platen can have its own induction hob.

Another embodiment disclosed herein includes a graphite sheet of either compressed peeled graphite particles, graphitized polymer, or a combination thereof disposed between an upper substrate and a lower substrate. The heat insulating material may be located between the graphite sheet and the lower substrate. The assembly of the upper substrate, the graphite sheet, the insulating layer and the lower substrate may be introduced into any type of article which may be desirable to be induction heated. Preferably, the lower substrate is disposed closer to the induction coil, and the upper substrate of the assembly is closest to the workpiece to be heated. In an alternative embodiment, if desired, the graphite sheet may be replaced with another material that is easy to bond to the magnetic field to generate heat. Further, the lower substrate is not limited to any particular material except that it is not a substance that is easy to bond with a magnetic field to generate heat. In this embodiment, the graphite sheet may vary from standard materials to graphite of the type mentioned above.

With respect to some preferred embodiments for using agglomerates of compressed exfoliated graphite particles ("CPEG") to induce a magnetic field, examples of independent exemplary properties may include graphite agglomerates having a thickness of at least 300 μm . Appropriate agglomerate thickness of CPEG was found to be less than about 1.5 mm (1500 μm). All thicknesses of 300 [mu] m to 1500 [mu] m are contemplated as disclosed herein. Preferably, the CPEG agglomerates have a density of greater than 1.22 g / cc. With respect to the graphite layer plane for inducing the magnetic field, an exemplary number of layer planes in the CPEG mass is at least 425,000. An example of the upper limit number of layer planes of graphene is up to about 3,000,000. One preferred range of graphene layer planes is 100,000 to 180,000, although all graphite layer planar numbers of 425,000 to 3,000,000 are considered herein.

For graphitized polymer embodiments, the preferred thickness is at least 45 microns. The upper limit of the lump thickness of the graphitized polymer is 300 mu m or less, and all thicknesses of 45 to 300 mu m are considered in this specification. The preferred number of graphene layer planes in the graphitized polymer agglomerate comprises at least 100,000. An example of a non-limiting upper limit may be less than 600,000. The preferred range of graphene layer planes for agglomerates of graphitized polymer may include from 250,000 to 600,000. Another independent property for graphitized polymer agglomerates can include electrical conductivity. In embodiments, the preferred in-plane electrical conductivity is at least 16000 S / cm. A non-limiting exemplary upper limit for in-plane electrical conductivity may be up to 20000 S / cm.

Further embodiments contemplated herein include forming a composite matrix, thereby providing various forms of ceramic precursor and / or glass precursors for producing precursors that are sufficiently inductively coupled to a magnetic field to generate a sufficient amount of heat. Since the graphite powder can be introduced into the precursor material, the composite can be used in the field of induction heating. An advantage of this embodiment is that the composite matrix can be further modified into any desired form. Likewise, the composite matrix can be introduced into any desired article.

Each embodiment disclosed herein may provide at least one of the following advantages: (1) increased in-plane thermal conductivity; (2) uniform heat transfer; (3) removal of hot spots; (4) decrease in dimensional change over time; (5) reducing the distortion of the cookware; (6) reducing the smear of cookware (due to exposure to moisture and oxygen associated with repeated use of certain types of cookware); (7) reducing the discoloration of cookware (related to acid rich foods and the reaction of surfaces of certain types of cookware); (8) reduction of vibration during induction cooking and removal of noise caused thereby; (9) Coatings on cookware show longer life; (10) Cost reduction; (11) weight reduction; (12) Elimination of the inevitable use of high ferrite based stainless steels for induction cooking; (13) Simple structure; And (14) A cooking appliance having improved resolution in heat regulation during heating and / or cooling.

Various embodiments may be practiced in any combination of these.

All patents and publications cited in this application are incorporated by reference in their entirety.

Although the present invention has been thus described, it will be obvious that the same may be varied in many ways. After you have read and understood the above specifications, you will be reminded of modifications and changes to the usual tape measure. It is intended that the invention be construed as including all such modifications and alterations insofar as they come within the scope of the appended claims or the equivalents thereof.

Claims (24)

As a cookware article,
A substrate comprising a lower surface of the cooking utensil;
An intermediate layer comprising a graphite layer having a sulfur content of less than 350 ppm; And
A cooking appliance article comprising a cooking surface disposed over an intermediate layer. The cooking apparatus according to claim 1, wherein the graphite has a density of at least 0.64 g / cm ³ . The cooking appliance according to claim 2, wherein the sulfur content is 200 ppm or less. The cooking apparatus according to claim 2, further comprising a heat insulating material disposed between the substrate and the intermediate layer. 3. The cooking utensil of claim 2, wherein the amount of graphite in the intermediate layer comprises an amount sufficient to generate heat upon exposure to a magnetic field at a frequency of at least 15 KHz. 2. The cooking utensil of claim 1, wherein the substrate comprises an amount of ferromagnetic material that is insufficient to be cooked by induction. The cooking utensil of claim 1, wherein the surface area of the graphite layer comprises at least 7 square inches. 2. The cooker of claim 1, wherein the substrate has a through plane thermal conductivity of less than about 75 W / mK. 2. The method of claim 1, wherein the substrate comprises a structure for supporting graphite in an intermediate layer, the structure comprising an effective amount of a material that can effectively couple to a cooking application upon exposure to a magnetic field of at least 15 KHz. Instrument. The cooking apparatus according to claim 1, wherein the Taber stiffness of the graphite is at least 30% higher in the machine direction of the graphite layer than in the transverse direction of the graphite layer. The cooker of claim 1, wherein the water pickup of the graphite layer comprises less than 30% by weight after immersion in water at room temperature for 2.5 hours at ambient pressure. 12. The article of claim 11, wherein the Teeber stiffness of the graphite is at least 25% higher in the machine direction of the graphite layer than in the transverse direction of the graphite layer. The cooking apparatus according to claim 1, further comprising a wire mesh embedded in the graphite layer. The cooking apparatus according to claim 1, wherein the graphite comprises at least one of a sheet of compressed peeled graphite particles, a graphitized polymer, and a combination thereof. As a cookware article,
A substrate comprising a lower surface of the cooking utensil;
An intermediate layer comprising a graphite layer having a thickness greater than 7 micrometers and a tear stiffness at least 25% higher in the machine direction than in the transverse direction; And
A cooking appliance article comprising a cooking surface disposed over an intermediate layer. As a cookware article,
A substrate comprising a lower surface of the cooking utensil;
An intermediate layer comprising a graphite layer having a water absorption of less than 30% by weight after immersion in water for more than 7 micrometers in thickness and in an ambient condition for 2.5 hours; And
A cooking appliance article comprising a cooking surface disposed over an intermediate layer. A graphite article having at least one major planar surface, the article having machine direction and transverse direction, the article having a Teeber stiffness of at least 25% higher in machine direction than in transverse direction. 18. An article according to claim 17, wherein at least one circumference of the article is surrounded by a heat insulating material having a thermal conductivity of less than 50 W / mK. As an article,
A substrate comprising a lower surface of the article;
An intermediate layer comprising a graphite layer having a sulfur content of less than 350 ppm; And
And an upper surface disposed over the intermediate layer. 20. The article of claim 19, wherein at least one of the substrate or the upper surface has a thermal conductivity of less than 75 W / mK. 20. The article of claim 19, further comprising a wire mesh embedded within the graphite layer. 20. The article of claim 19, wherein the graphite comprises at least one of a sheet of compressed peeled graphite particles, a graphitized polymer, and combinations thereof. 20. An article according to claim 19, wherein the graphite has at least one major planar surface, the graphite has machine direction and transverse direction, and the Teabor stiffness of the graphite is at least 25% higher in the machine direction than in the transverse direction. 23. The article of claim 22 having less than 30 weight percent water uptake after 2.5 hours immersion in water at ambient conditions.

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